Komatsu sk1020 5 na skid steer loader service repair manual sna60001 and up

CEBM013902
Shop
Manual
SK1020-5N
SK1020-5NA
SKID STEER LOADER
SERIAL NUMBERS SK1020-5N A70001 and up
SK1020-5NA A60001 and up
ENGINE S4D98E-2
®
www.KomatsuAmerica.com

FOREWORD CONTENTS
00-2 c SK1020-5N, SK1020-5NA
12
CONTENTS 00
01 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-1
10 STRUCTURE, FUNCTION AND MAINTENANCE STANDARD . . . . . . . . . . . . . . . . . . . . 10-1
20 STANDARD VALUE TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1
30 TESTING AND ADJUSTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40-1
40 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-1
50 DISASSEMBLY AND ASSEMBLY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50-1
90 DIAGRAMS AND SCHEMATICS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90-1

FOREWORD SAFETY
SK1020-5N, SK1020-5NA 00-3 c
12
SAFETY 00
SAFETY NOTICE 00
GENERAL PRECAUTIONS 00
Mistakes in operation are extremely dangerous. Read the OPERATION & MAINTENANCE MANUAL carefully BEFORE
operating the machine.
1. Before carrying out any greasing or repairs, read all the precautions given on the decals which are fixed to the machine.
2. When carrying out any operation, always wear safety shoes and helmet. Do not wear loose work clothes, or clothes with
buttons missing.
• Always wear safety glasses when hitting parts with a hammer.
• Always wear safety glasses when grinding parts with a grinder, etc.
3. If welding repairs are needed, always have a trained, experienced welder carry out the work. When carrying out welding
work, always wear welding gloves, apron, glasses, cap and other clothes suited for welding work.
4. When carrying out any operation with two or more workers, always agree on the operating procedure before starting.
Always inform your fellow workers before starting any step of the operation. Before starting work, hang "UNDER
REPAIR" signs on the controls in the operator's compartment.
5. Keep all tools in good condition and learn the correct way to use them.
6. Decide a place in the repair workshop to keep tools and removed parts. Always keep the tools and parts in their correct
places. Always keep the work area clean and make sure that there is no dirt or oil on the floor. Smoke only in the areas
provided for smoking. Never smoke while working.
PREPARATIONS FOR WORK 00
1. Before adding oil or making repairs, park the machine on hard, level ground, and block the wheels or tracks to prevent the
machine from moving.
2. Before starting work, lower blade, ripper, bucket or any other work equipment to the ground. If this is not possible, insert
the safety pin or use blocks to prevent the work equipment from falling. In addition, be sure to lock all the control levers
and hang warning signs on them.
3. When disassembling or assembling, support the machine with blocks, jacks or stands before starting work.
IMPORTANT SAFETY NOTICE 00
Proper service and repair is extremely important for the safe operation of your machine. The service and repair techniques
recommended and described in this manual are both effective and safe methods of operation. Some of these operations
require the use of tools specially designed for the purpose.
To prevent injury to workers, the symbol is used to mark safety precautions in this manual. The cautions
accompanying these symbols should always be followed carefully. If any dangerous situation arises or may possibly arise,
first consider safety, and take the necessary actions to deal with the situation.
WARNING! Never modify, weld, cut, or drill on any part of a ROPS structure. Doing so may weaken the
structure which could lead to possible failure in a rollover situation

FOREWORD SAFETY
00-4 c SK1020-5N, SK1020-5NA
4. Remove all mud and oil from the steps or other places used to get on and off the machine. Always use the handrails, lad-
ders or steps when getting on or off the machine. Never jump on or off the machine. If it is impossible to use the handrails,
ladders or steps, use a stand to provide safe footing.
PRECAUTIONS DURING WORK 00
1. When removing the oil filler cap, drain plug or hydraulic pressure measuring plugs, loosen them slowly to prevent the oil
from spurting out. Before disconnecting or removing components of the oil, water or air circuits, first remove the pressure
completely from the circuit.
2. The water and oil in the circuits are hot when the engine is stopped, so be careful not to get burned. Wait for the oil and
water to cool before carrying out any work on the oil or water circuits.
3. Before starting work, remove the leads from the battery. ALWAYS remove the lead from the negative (-) terminal first.
4. When raising heavy components, use a hoist or crane. Check that the wire rope, chains and hooks are free from damage.
Always use lifting equipment which has ample capacity. Install the lifting equipment at the correct places. Use a hoist or
crane and operate slowly to prevent the component from hitting any other part. Do not work with any part still raised by
the hoist or crane.
5. When removing covers which are under internal pressure or under pressure from a spring, always leave two bolts in
position on opposite sides. Slowly release the pressure, then slowly loosen the bolts to remove.
6. When removing components, be careful not to break or damage the wiring, Damaged wiring may cause electrical fires.
7. When removing piping, stop the fuel or oil from spilling out. If any fuel or oil drips on to the floor, wipe it up immediately.
Fuel or oil on the floor can cause you to slip, or can even start fires.
8. Gasoline or other fuels should never be used to clean parts. Clean part with appropriate solvents.
9. Be sure to assemble all parts again in their original places. Replace any damaged part with new parts.
• When installing hoses and wires, be sure that they will not be damaged by contact with other parts when the machine
is being operated.
10. When installing high pressure hoses, make sure that they are not twisted. Damaged tubes are dangerous, so be extremely
careful when installing tubes for high pressure circuits. Also check that connecting parts are correctly installed.
11. When assembling or installing parts, always use the specified tightening torques. When installing protective parts such as
guards, or parts which vibrate violently or rotate at high speed, be particularly careful to check that they are installed
correctly.
12. When aligning two holes, never insert your fingers or hand. Be careful not to get your fingers caught in a hole.
13. When measuring hydraulic pressure, check that the measuring tool is correctly assembled before taking any
measurements.
14. Take care when removing or installing the tracks of track-type machines. When removing the track, the track separates
suddenly, so never let anyone stand at either end of the track.
15. When jump starting the machine, only use a machine of similar size and voltage. Never use a arc welder or other electrical
generating equipment to jump start the machine. Carefully review the safety and procedures for jump starting the
machine.

FOREWORD GENERAL
SK1020-5N, SK1020-5NA 00-5 c
12
GENERAL 00
This shop manual has been prepared as an aid to improve the quality of repairs by giving the serviceman an accurate
understanding of the product and by showing him the correct way to perform repairs and make judgements. Make sure you
understand the contents of this manual and use it to full effect at every opportunity.
This shop manual mainly contains the necessary technical information for operations performed in a service workshop. For
ease of understanding, the manual is divided into the following sections. These sections are further divided into each main
group of components.
GENERAL
This section lists the general machine dimensions, performance specifications, component weights, and fuel, coolant and
lubricant specification charts.
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
This section explains the structure and function of each component. It serves not only to give an understanding of the
structure, but also serves as reference material for troubleshooting. In addition, this section gives the judgement standards
when inspecting disassembled parts.
STANDARD VALUE TABLE
This section explains the standard values for new machine and judgement criteria for testing, adjusting and
troubleshooting. This standard value table is used to check the standard values in testing and adjusting and to judge parts
in troubleshooting.
TESTING AND ADJUSTING
This section explains checks to be made before and after performing repairs, as well as adjustments to be made at
completion of the checks and repairs.
TROUBLESHOOTING
Troubleshooting charts correlating “Problems” to “Causes” are included in this section.
DISASSEMBLY AND ASSEMBLY
This section explains the order to be followed when removing, installing, disassembling or assembling each component,
as well as precautions to be taken for these operations.
DIAGRAMS AND SCHEMATICS
This section has the foldout drawings for the machine.
NOTICE
The specifications contained in this shop manual are subject to change at any time and without any advance notice. Contact
your distributor for the latest information.

FOREWORD HOW TO READ THE SHOP MANUAL
00-6 c SK1020-5N, SK1020-5NA
12
HOW TO READ THE SHOP MANUAL 00
Volumes 00
Shop manuals are issued as a guide to carrying out repairs.
They are divided as follows:
Chassis volume: Issued for every machine model
Engine volume: Issued for each engine series
Electrical volume: Each issued as one to cover all models
Attachment volume: Each issued as one to cover all models
These various volumes are designed to avoid duplication of
information. Therefore to deal with all repairs for any model,
it is necessary that chassis, engine, electrical and attachment
be available.
Distribution and Updating 00
Any additions, amendments or other changes will be sent to
your distributors. Get the most up-to-date information before
you start any work.
Filing Method 00
1. See the page number on the bottom of the page. File the
pages in correct order.
2. Following examples show how to read the page number:
Example:
10 - 3
Item number (10. Structure and Function)
Consecutive page number for each item
3. Additional pages: Additional pages are indicated by a
hyphen (-) and numbered after the page number. File as
in the example.
Example:
Revised Edition Mark 00
When a manual is revised, an edition mark (bcd…) is
recorded on the bottom outside corner of the pages.
Revisions 00
Revised pages are shown at the LIST OF REVISED PAGES
between the title page and SAFETY page.
Symbols 00
So that the shop manual can be of ample practical use,
important places for safety and quality are marked with the
following symbols.
10-4
10-4-1
Added pages
10-4-2
10-5
Symbol Item Remarks
Safety
Special safety precautions are
necessary when performing the
work.
★ Caution
Special technical precautions or
other precautions for preserving
standards are necessary when
performing the work.
Weight
Weight of parts or systems.
Caution necessary when
selecting hoisting wire or when
working posture is important,
etc.
Tightening
torque
Places that require special
attention for tightening torque
during assembly.
Coat
Places to be coated with
adhesives and lubricants etc.
Oil, water
Places where oil, water or fuel
must be added, and the capacity.
Drain
Places where oil or water must
be drained, and quantity to be
drained.

01 GENERAL
01-1C
DIMENSION DRAWINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-2
Machine Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-2
Working Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-3
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-4
WEIGHT TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-6
FUEL COOLANT AND LUBRICANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-7
SERVICE NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01-8
SK1020-5N, SK1020-5NA

GENERAL DIMENSION DRAWINGS
01-2 2 SK1020-5N, SK1020-5NA
12
DIMENSION DRAWINGS
Machine Dimensions
* Weights, lengths and widths will vary depending on the attachment used on the machine.
* * With standard bucket, full fuel tank and 80 kg (176 lb) operator.
Item Unit
SK1020-5N
Standard Bucket 1880 mm (74 in)
SK1020-5N
Pallet Forks 1219 mm (48 in)
* * Operating weight kg (lb) 3435 (7,573) 3435 (7,573)
Bucket capacity (standard SAE rated) m3
(yd3
) 0.47 (0.61) N/A
Diesel engine --- KOMATSU 4D98E-1FD [4SD98E-1FD Optional Turbo]
Engine horsepower kW @ rpm 52.2 @ 2800 [60.0 @ 2800]
A * Overall length mm (in) 3547 (140) 3547 (140)
B * Overall width mm (in) 1880 (75) 1880 (75)
C Overall height mm (in) 2230 (88) 2230 (88)
D Cab height mm (in) 2050 (81) 2050 (81)
E Ground clearance (chassis) mm (in) 237 (9.3) 237 (9.3)
F Ground clearance (drive motor) mm (in) 190 (7.5) 190 (7.5)
G Axle width (no tires) mm (in) 1504 (59.2) 1504 (59.2)
H Axle length (center to center) mm (in) 1162 (46) 1162 (46)
I Front axle center to bucket cutting edge mm (in) 1358 (53.5) 1358 (53.5)
J Rear axle center to counter weight face mm (in) 1027 (40.4) 1027 (40.4)

GENERAL DIMENSION DRAWINGS
SK1020-5N, SK1020-5NA 01-3 2
12
Working Ranges
* All dimensions, weights and performance values based on SAE J72c and J742b standards. Static tipping load and operating
weight shown include 12.00 X 16.5 8PR tires, lubricant, coolant, full fuel tank, ROPS canopy and operator. Machine stabil-
ity and operating weight are affected by counterweight, tire size and other attachments.
Bucket
Base Machine
with 1880 mm (74 in) bucket
Base Machine with 120 kg (265 lb)
weights and 1880 bucket
Base Machine with 120 kg (265 lb)
weights and 1291 mm (48 in) pallet
forks
Bucket capacity (SAE rated) 0.47m3
(0.61 yd3
) 0.47m3
(0.61 yd3
) N/A N/A
Bucket width 1880 mm (74 in) 1880 mm (74 in) N/A N/A
Bucket weight 1219 mm (48 in) pallet
fork weights
211 kg (465 lb 211 kg (465 lb 172 kg (378 lb)
Stacked tipping load 1814 kg (4,000 lb) 1916 kg (4,400 lb) 1309 kg (2,880 lb)
Operating capacity - 50% of tipping
load
907 kg (2,000 lb) 998 kg (2,200 lb) 655 kg (1,440 lb)
Dump clearance, maximum height
and 45o
dump angle
2300 mm (90.5 in) 2300 mm (90.5 in) N/A N/A
Height to bucket hinge pin 3100 mm (122 in) 3100 mm (122 in) 3100 mm (122 in)
Reach at maximum height and 45o
dump angle
690 mm (27.1 in) 690 mm (27.1 in) N/A N/A
Operating height (fully raised) 4100 mm (161 in) 4100 mm (161 in) N/A N/A
Clearance circle-front 2265 mm (89.2 in) 2265 mm (89.2 in) 2286 mm (90 in)
Clearance circle-rear 1650 mm (64.9 in) 1650 mm (64.9 in) 1650 mm (64.9 in)
Operating weight 3435 mm (7,573 lb) 3560 mm (7,848 lb) 3528 kg (7,761 lb)

GENERAL SPECIFICATIONS
01-4C SK1020-5N, SK1020-5NA
12
SPECIFICATIONS
Engine
Model Komatsu 4D98E-1FD [4SD98E-1FD Optional Turbo]
Type Diesel engine 4 cycle
Bore and Stroke 98 x 110 (3.85 x 4.334 in)
Number of cylinders 4 cylinder
Displacement 3.4 L. (203 in3
)
Combustion Direct injection
Aspiration Natural or [Turbo charged]
Power Rating
SAE J1349 52.2 kW (70 hp) [61.9 kW (83 hp) Turbo] @ 2500 rpm
80/1269/EC 52.2 kW (70 hp) [60.0 kW (80 hp) Turbo] @ 2800 rpm
Maximum torque 286 N·m (211 lbf ft) @ 1600 rpm
Cooling system Antifreeze coolant and distilled water
Air filter Dry type with safety element
Starting system Electric motor with pre-heating air system for cold weather 0°C (32°F)
Transmission
Type Hydrostatic
Pumps 2 x Variable displacement with 2 stage and APC system
Motors 2 x Axial pistons with two speeds
Final transmission with heavy duty type roller chains immersed in oil bath connected to the four drive axles
Speeds
Working: 10.0 kg/h (6.5 mph)
Travel: 16.0 km/h (10.0 mph)
Sealed wet-disk parking brakes with automatic engagement when operator restraint bar is raised
Hydraulic
System
Type Komatsu CLSS (Closed Load Sensing System)
Pump Gear
Maximum flow Auxiliary hydraulic: 80.0 L/min (21.0 gal/min)
Maximum pressure Auxiliary hydraulic: 210 bar (3,045 psi)
Control valve 3 elements fully Servo-controlled
High Flow Auxiliary Hydraulic System “SUPER FLOW” (optional)
Maximum flow 130 L/min (34 gal/min)
Maximum pressure 210 bar (3,045 psi)
Control valve 4 elements
Loader
Performance Without Counterweights
Operating load (ISO 5998) 907 kg (2,000 lb)
Tipping load (ISO 8313) 1814 kg (4,000 lb)
Bucket breakout force (ISO 8313) with short lip bucket 2290 kg (5,038 lb)
Bucket breakout force (ISO 8313) with long lip bucket 1940 kg (4,279 lb)
Maximum hydraulic lift capacity (ISO 8313) 3082 kg (6,796 lb)
Refill
Capacities
Hydraulic tank 50.0 L (13.0 US gal)
Fuel tank 73.0 L (19.0 US gal)
Chain case 32.0 L (8.3 US gal)
Engine oil 12.5 L (3.2 US gal)
Engine coolant 8.0 L (2.0 US gal)

GENERAL SPECIFICATIONS
SK1020-5N, SK1020-5NA 01-5 2
Tires 12 - 16.5 10PR heavy duty flotation tires
12 - 16.5 (Airboss) segmented solid tires
33 x 15.5 - 16.5 10PR super wide flotation tires
Electrical
Rated voltage 12 V
Battery 100 Ah
Alternator 40A

GENERAL WEIGHT TABLE
01-6C SK1020-5N, SK1020-5NA
12
WEIGHT TABLE
Unit: kg (lb)
WARNING! This weight table is a guide for use when transporting or handling equipment components
Machine Model SK1020-5NA SK1020-5N
Engine assembly - Muffler - Exhaust pipe 235 (518) 235 (518)
Radiator 35 (77) 38 (84)
Hydraulic tank (without oil) 25 (55) 25 (55)
Engine hood 18.5 (41) 18.5 (41)
Operator compartment (without seat) 215 (474) 215 (474)
Seat
• Standard
• With adjustable suspension
10 (22)
16 (35)
10 (22)
16 (35)
Engine-pump group 238-335 (525-739) 238-335 (525-739)
Piston pump
• Standard
• High-flow
91 (201)
98 (216)
91 (201)
98 (216)
Wheel assembly (standard only) 52 (115) 52 (115)
Control valve
• 3-spool (Standard)
• 4-spool (High-flow
21 (46)
24 (53)
21 (46)
24 (53)
Work equipment
• Arm
• Work equipment support
• Bucket
• Tilt back cylinder
• Dump cylinder
325 (717)
80 (176)
205 (452)
25 (55)
15 (33)
325 (717)
80 (176)
205 (452)
25 (55)
15 (33)

GENERAL FUEL COOLANT AND LUBRICANTS
SK1020-5N, SK1020-5NA 01-7 2
12
FUEL COOLANT AND LUBRICANTS
★ ASTM D975 No. 1
RESERVOIR
TYPE OF
FLUID
AMBIENT TEMPERATURE CAPACITY l (Qts & Gal)
-22 -4 14 32 50 68 86 104°F
-30 -20 -10 0 10 20 30 40°C
First filling Change
Engine oil pan
101 l
(2.64 US gal)
101 l
(2.64 US gal)
OIL
API CI-4
SAE 10W
SAE 30
SAE 40
SAE 10W-30
SAE 5W-30
Hydraulic system and
hydrostatic transmission
OIL
API CI-4
501 l
(13.2 US gal)
321 l
(8.4 US gal)
SAE 10W
SAE 5W-30
Final transmission case
(each)
OIL
API CI-4
13.15 l
(3.5 US gal)
13.15 l
(3.5 US gal)
SAE 10W-30
Fuel tank Diesel fuel
721 l
(19.0 US gal)
★
ASTM D975 No. 2
Engine cooling system --- 151 l (3.9 US gal)
ETHELENE GLYCOL BASE

GENERAL SERVICE NOTES
01-8C SK1020-5N, SK1020-5NA
12
SERVICE NOTES
• Use only Komatsu genuine parts on this machine
• Do not mix different types of oils.
• Unless specified otherwise, the oils and the coolant used by Komatsu to fill the tanks before delivery of the machine are as
follows:
Item Specifications
• Engine oil
SAE 10W-30
API classification CI-4
• Hydraulic system and hydrostatic
transmission oil
SAE 10W
• Final transmission oil
SAE 10W-30
• Fuel
Ambient temperature above - 10°C (14°F)
ASTM D975 No. 2 diesel fuel
Ambient temperature below - 10°C (14°F)
ASTM D975 No. 1 diesel fuel
• Radiator
Permanent, ethylene glycol-based antifreeze, with
corrosion inhibitor for protection up to -36°C (-33°F)

10-1 2
10 STRUCTURE, FUNCTION AND
MAINTENANCE STANDARD
1245
WORK EQUIPMENT PIVOT POINT CLEARANCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
WHEEL DRIVE SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5
Power Train Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5
Transmission System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6
Wheel Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
DRIVE MOTOR SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8
Motor Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8
Motor Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9
Motor Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10
HYDRAULIC PUMPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13
Drive Dampener . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13
Maintenance Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13
Charge Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-14
HST Pump LPV45 + 45 (Standard and High Flow) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-15
Pump Internal View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17
Operation of Main Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-18
Shuttle Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-20
SAFETY VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-21
Suction Safety Valve Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-21
Charge Safety Valve Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-24
ANTI ENGINE-STALL VALVE (AS VALVE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-26
AS Valve Maintenance Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-28
CONTROL VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-29
Standard 3-Spool Valve Port Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-29
Valve-Sectional Views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-30
Super High-Flow 4-Spool Valve Port Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-32
Valve-Sectional Views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-33
Control Valve Maintenence Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-36
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-37
Control Valve (Standard) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-44
Control Valve (Super High-Flow) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-46
CLOSED CENTER LOAD SENSING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-48
Pressure Compensation Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-48
Hydraulic Circuit Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-50
System in Series Circuit Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-51
Self Leveling Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-52
System in Series-Parallel Circuit Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-53
Pressure Compensation Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-54
SK1020-5N, SK1020-5NA

10-2 2 SK1020-5N, SK1020-5NA
STRUCTURE, FUNCTION AND
MAINTENANCE STANDARD TABLE OF CONTENTS
Dividing Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-55
SOLENOID VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-56
Valve Group ST1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-56
ACCUMULATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-57
PATTERN CHANGE VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-58
Maintenance Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-58
Pattern Options Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-60
Pattern ISO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-60
Pattern Optional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-60
R.H. PPC VALVE (STANDARD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-61
Equipment Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-61
R.H. PPC Valve Maintenance Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-62
R.H. PPC VALVE (PATTERN CHANGE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-64
Equipment and Travel Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-64
L.H. PPC VALVE (STANDARD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-67
Travel Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-67
Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-68
L.H. PPC VALVE (PATTERN CHANGE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-72
Equipment and Travel Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-72
Pattern Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-73
CYLINDERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-76
Boom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-76
Bucket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-76

SK1020-5N, SK1020-5NA 10-3 2
MAINTENANCE STANDARD WORK EQUIPMENT PIVOT POINT CLEARANCES
WORK EQUIPMENT PIVOT POINT CLEARANCES

10-4 2 SK1020-5N, SK1020-5NA
MAINTENANCE STANDARD WORK EQUIPMENT PIVOT POINT CLEARANCES
12
Unit: mm (in)
No. Check Item clearance
Criteria Remedy
Standard
size
Tolerance Minimum
clearances
Clearance
limit
Replace
if
damaged
or
deformed
Shaft Hole
1
Between bushing and
mounting pin on work
equipment
35 (1.4)
-0.01 (0.0004)
-0.05 (0.002)
+0.072 (0.003)
+0.134 (0.005)
0.082 (0.003)
0.184 (0.007)
1.0 (0.04)
2
Between bushing and
mounting pin on fulcrum arm
35 (1.4)
-0.01 (0.0004)
-0.05 (0.002)
+0.072 (0.003)
+0.134 (0.005)
0.082 (0.003)
0.184 (0.007)
1.0 (0.04)
3
Between bushing and
mounting pin lift cylinder (top
and bottom size)
35 (1.4)
-0.01 (0.0004)
-0.05 (0.002)
+0.072 (0.003)
+0.134 (0.005)
0.082 (0.003)
0.184 (0.007)
1.0 (0.04)
4
Between bushing and
mounting pin bucket cylinder
(top side)
35 (1.4)
-0.01 (0.0004)
-0.05 (0.002)
+0.072 (0.003)
+0.134 (0.005)
0.082 (0.003)
0.184 (0.007)
1.0 (0.04)
5
Between bushing and
mounting pin bucket cylinder
(bottom side)
35 (1.4)
-0.01 (0.0004)
-0.05 (0.002)
+0.072 (0.003)
+0.134 (0.005)
0.082 (0.003)
0.184 (0.007)
1.0 (0.04)

SK1020-5N, SK1020-5NA 10-5 2
MAINTENANCE STANDARD WHEEL DRIVE SYSTEM
WHEEL DRIVE SYSTEM
Power Train Flow
1. Engine 5. High-flow solenoid valve
2. Hydraulic pump 6. L.H. final drive
3. Control valve 7. R.H. final drive
4. Solenoid valve 8. Axle
A. Servo control
B. Speed increment
C. Parking brake

10-6 2 SK1020-5N, SK1020-5NA
12
Transmission System
1. L.H. final drive 3. Rear drive chain
2. Front drive chain 4. Master link

SK1020-5N, SK1020-5NA 10-7 2
12
Wheel Axles
1. Front wheel 5. Front drive chain
2. Axle housing 6. Rear wheel
3. Sprocket 7. Rear drive chain
4. Axle shaft

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10-8 2 SK1020-5N, SK1020-5NA
MAINTENANCE STANDARD DRIVE MOTOR SYSTEM
12
DRIVE MOTOR SYSTEM
Motor Ports
L.H. Final Drive R.H. Final Drive
a. A Port - To hydraulic pump (PA2 port) a. A Port - To hydraulic pump (PA2 port)
b. B Port - To hydraulic pump PB2 port) b. B Port - To hydraulic pump PB2 port)
c. PP1 Port - From solenoid valve group ST1
(A Port) (2nd speed)
c. PP1 Port - From solenoid valve group ST1
(A Port) (2nd speed)
d. PP2 Port - From solenoid valve group ST1
(C Port (parking brake)
d. PP2 Port - From solenoid valve group ST1
(C Port (parking brake)
e. DR Port - To hydraulic tank e. DR Port - To hydraulic tank

SK1020-5N, SK1020-5NA 10-9 2
12
Motor Structure
1. Shaft 10. Brake piston 19. Swash plate 28. Plug
2. Bearing 11. Plate 20. Shaft 29. Spool
3. Bearing 12. Cylinder block 21. Flange 30. Plug
4. Housing body 13. Bearing 22. Flange 31. Spring
5. Pin 14. Spring 23. Collar
6. Gear 15. Brake piston 24. Gasket
7. Pin 16. Brake spring 25. Plug
8. Gear 17. Bushing 26. Spring
9. Shoe 18. Retainer plate 27. Spool

10-10 2 SK1020-5N, SK1020-5NA
12
Motor Operations
Description
The drive motor consists of:
• 2-speed hydraulic motor
• Selector valve
• Reduction gearing
Motor Function
The hydraulic drive motor is an axial piston type motor that converts hydraulic energy supplied by the main hydraulic pump
into usable rotary motion.
Operation
The hydraulic oil arriving from the selector valve is sent on to the valve
plate (1). When the oil is sent to port “A” of the valve, it flows into the
corresponding port on the cylinder block (2) and presses against the
pistons (3). This pressure is converted into rotary motion by a swash
plate (4) and transmitted to the shaft (5). The shaft and the cylinder
block have been integrated into one piece by means of spined teething.
The return oil is sent to the pump through port “B”. Rotation in the
opposite direction is achieved by sending the oil to port “B” instead of
to port “A”.
Varying The Displacement
The swash plate (4), which has two surfaces “A” and “B” on the side opposite the sliding side for the shoes (6), is supported
by two bearings (7) attached to the body of the motor (8). The position of the bearings is eccentric with respect to the axis of
the shaft and when running at a low speed the surface “A” remains in contact with the body of the motor through the pressure
exerted by the pistons (3) and by the force of a spring (9) mounted in the cylinder block (2). The angle of the swash plate is α.
When an increase in speed is demanded, the oil is sent under pressure to the command piston (10). The command piston
(10) moves to the left until the surface “B” makes contact with the housing and the angle of the swash plate becomes β (the
displacement of the motor is reduced).

Komatsu sk1020 5 na skid steer loader service repair manual sna60001 and up

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Komatsu sk1020 5 na skid steer loader service repair manual sna60001 and up